Charge pump regulators can form an important part of many communication devices, such as DSL modems, wireless portable devices, such as cellular telephones, tablets, phablets, laptops, and the like. For example, a mobile communications device without multiple supply rails may potentially use a charge pump regulator to provide multiple supply voltage levels by selectively charging and discharging one or more capacitors. However, conventional charge pump regulators are not easily adaptable for use in many mobile communication devices.
Typically, conventional charge pump regulators are unable to generate the multiple voltage reference levels that are required by components such as Class-G amplifiers within many mobile communication devices. A Class-G amplifier driving an audio headset of a cellular telephone, for instance, may require multiple sets of supply voltages, which a single conventional charge pump may be unable to provide. Moreover, conventional charge pump regulators using multiple fly-back capacitors or switching regulators may often be too inefficient or costly for many mobile communication devices. Many mobile communication devices may require a single charge pump regulator that can generate multiple sets of reference voltages, and can smoothly transition between these multiple reference voltages in a power-efficient and reliable manner.
A charge-pump low-dropout (LDO) regulator may maintain regulation with a small difference between the regulated output voltage and a reference voltage such as an input supply voltage. The low dropout voltage and low quiescent current of charge-pump LDO regulators may make the charge-pump LDO regulators a good fit for many portable and wireless applications.